Question

How do I use local database in windows phone 7 to save just a value, then retrieve that value every time the app is loaded (opened)?

Answer 1

If all you want to do is store a value for retrieval, then I would recommend using IsolatedStorage, particularly the ApplicationSettings class.

An example of it’s usage:

using System.IO.IsolatedStorage;

//storing value
int someValue = 10;
IsolatedStorageSettings.ApplicationSettings.Add("MyKey",someValue);

//write or update value
IsolatedStorageSettings.ApplicationSettings["MyKey"] = someValue;

//write to disk
IsolatedStorageSettings.ApplicationSettings.Save();


//reading value
if(IsolatedStorageSettings.ApplicationSettings.Contains("MyKey"))
{
   int readValue = (int) IsolatedStorageSettings.ApplicationSettings["MyKey"];
}   

Mango now offers MSSqlCE support, but for a set of values, it’s overkill. A database is more appropriate if you need to store relational data, as opposed to persisting user/application settings.

While IsolatedStorage is nice, it can be expensive to read and write to. Avoid reading from IsolatedStorage from your UI thread, which will cause your app to appear to be unresponsive.